Agent Of Gray Mold Research Articles

Acinetobacter calcoaceticus SJ19 and Bacillus safensis SJ4, two Algerian rhizobacteria protecting tomato plants against Botrytis cinerea and promoting their growth

BackgroundBotrytis cinerea, the causal agent of grey mould, is a polyphagous fungus that infects a wide range of plants, including tomato. In many countries, including Algeria, the management of grey mould is a challenging problem, even with chemical control. This necessitates the search for other strategies. The objective of this study was to evaluate the biocontrol potential of two rhizospheric bacterial isolates for the protection of tomato against B. cinerea.ResultsOn tomato plants, the two bacterial isolates consistently provided high levels of protection (on average 72.1% for SJ19 and 52.3% for SJ4). Their applications as a 1:1 mixture reinforced their effect (87.8% protection), indicating their compatibility and a potential use as a consortium. In vitro, the isolates significantly inhibited the mycelial growth of B. cinerea strains, both through direct confrontation in dual-culture assays (12–69% inhibition) and through the production of volatile compounds (36–46% inhibition). The two isolates, applied as seed treatment and as drench on seedlings, also showed strong growth-promoting effects on tomatoes. They substantially increased the length and fresh weight of shoots and roots, as well as stem diameter, leaf number and chlorophyll content, compared to untreated plants.ConclusionThe two bacteria tested in this study showed a high potential for use as biostimulants and as biofungicides against tomato grey mould.

Colonization of Solanum melongena and Vitis vinifera Plants by Botrytis cinerea Is Strongly Reduced by the Exogenous Application of Tomato Systemin.

Plant defense peptides are able to control immune barriers and represent a potential novel resource for crop protection. One of the best-characterized plant peptides is tomato Systemin (Sys) an octadecapeptide synthesized as part of a larger precursor protein. Upon pest attack, Sys interacts with a leucine-rich repeat receptor kinase, systemin receptor SYR, activating a complex intracellular signaling pathway that leads to the wound response. Here, we demonstrated, for the first time, that the direct delivery of the peptide to Solanum melongena and Vitis vinifera plants protects from the agent of Grey mould (Botrytis cinerea). The observed disease tolerance is associated with the increase of total soluble phenolic content, the activation of antioxidant enzymes, and the up-regulation of defense-related genes in plants treated with the peptide. Our results suggest that in treated plants, the biotic defense system is triggered by the Sys signaling pathway as a consequence of Sys interaction with a SYR-like receptor recently found in several plant species, including those under investigation. We propose that this biotechnological use of Sys, promoting defense responses against invaders, represents a useful tool to integrate into pest management programs for the development of novel strategies of crop protection.

Characterization of tebuconazole resistance in Botrytis cinerea from tomato plants in China

Fungal pathogen Botrytis cinerea, the casual agent of gray mold of vegetables and fruits, has a high risk of developing resistance to fungicide. Tebuconazole, one kind of demethylation inhibitor (DMI) fungicides, has been increasingly applied for the control of tomato gray mold in China. However, very limited information is available on the resistance profile of B. cinerea to tebuconazole. In this study, the baseline sensitivity of B. cinerea to tebuconazole was determined based on 138 isolates from field sites having no history of DMI usage, with a mean EC50 value of 0.29 μg/mL. Another 159 B. cinerea isolates collected in the greenhouse and field from 2011 to 2016 were demonstrated to have a shifted sensitivity to tebuconazole, with a mean EC50 value of 0.66 μg/mL. EC50 values of 10 B. cinerea isolates with reduced sensitivity to tebuconazole were greater than 1.56 μg/mL, and these reduced-sensitive isolates had a fitness penalty in sporulation and conidial germination, but showed similar mycelial growth rate and pathogenicity with those of the sensitive isolates. Positive cross-resistance was observed only between tebuconazole and the other two DMIs difenoconazole and prochloraz, but not between tebuconazole and the non-DMIs iprodione, procymidone, or fludioxonil. In reduced-sensitive isolates, no amino acid variation was found in the BcCYP51 protein. When exposed to tebuconazole, the expression level of BcCYP51 increased in these reduced-sensitive B. cinerea isolates as compared to sensitive ones, thus contributing to the reduced sensitivity of the pathogen to tebuconazole. Additionally, the nucleotide mutation observed in the 1200 bp upstream region of BcCYP51 had no correlation with the development of fungicide resistance in B. cinerea isolates. These findings will be helpful for the understanding of DMI resistance mechnism in B. cinerea.

Antifungal activity of five chemical and two biological fungicides for the management of Botrytis cinerea, causal agent of Gray Mold in Strawberry

Gray mold, caused by Botrytis cinerea, is one of the most important plant diseases in Strawberry in Peru. Because of its high variability and its pathogenic characteristics, proper fungicides use is essential to control this disease. The aim of this study was to evaluate the effect of five chemical fungicides: Tryfloxistrobin (0.0625%), Pyrimethanil + Fluopyram (0.1%), Pyrimethanil (0.1%), Fenhexamid (0.135%) and Carbendazim (0.125%), and two biological fungicides: Bacillus subtilis QST713 (0.75%) and Bacillus pumilus QST2808 (0.75%) in laboratory and field conditions. In the laboratory phase, the inhibition of mycelial growth was measured by evaluating diameter growth at 4 DAI (p≤0.05). Furthermore, conidial germination inhibition was evaluated in two different ways. First, one hundred conidia were placed in sterile water with fungicide and evaluated at 24 HAI (p≤0.05). Second, the number of CFUs was counted in poisoned PDA medium at 3 DDI. The doses 1x106 and 125 conidia/mL were used for each test respectively. The field experiment was in Aucallama, Huaral. Chemical and biological fungicides were sprayed in a strawberry cultivar Aromas. Twelve harvests were done. The results showed that chemical fungicides; Trifloxystrobin, Pyrimethanil + Fluopyram, Pyrimethanil, Fenhexamid and the biological fungicide Bacillus subtilis QST713 had considerable activity against Botrytis cinerea in most of the variables assessed. These results will contribute to the evaluation of the potential of each one of these fungicides for the management of Botrytis cinerea.

English

The use of municipal solid waste compost in agriculture has known a particular interest because of its favorable effects on soil, on cultures and on environment. Treatment of plants with compost or compost extract or even their root or foliar inoculation with Trichoderma harzianum Tcomp, isolated from compost, were the most three efficient treatments against three strains of Botrytis cinerea agent of gray mold of tomato. These treatments induced similar suppressive effects in term of severity for the three strains of B. cinerea (B2, Bf3 and BP1), ranging between 0.9 and 1.3 for B2, or between 1 and 1.3 for Bf3 or even between 1.1 and 1.2 for BP1. Conidia productions for these three treatments are also similar for the three strains of B. cinerea, ranging between 1.02 and 1.09 10 4 conidia / cm 2 for B2, or between 1.06 and 1.08 10 4 conidia / cm 2 for Bf3 or even between 1.13 and 1.27 10 4 conidia / cm 2 for Bp1. The antagonists used in this study have efficiently suppress gray mold of tomato to varying degrees according to the antagonist itself (Trichoderma harzianum or Ulocladium atrum) and also to the inoculation method for T. harzianum, since each strain acts using one or more modes of action. Thus, TH1 and Tcomp strains act primarily by inducing the SR (systemic resistance) and LR (local resistance). Ulocladium atrum isolated from compost reduced B. cinerea by direct inhibition of conidia production. Whereas for T. harzianum Ttom, other mechanisms are involved. The effect of compost on B. cinerea, which is a foliar pathogen, is unusual and is due to the induction of tomato systemic resistance plants that is associated with the presence of a population of T. harzianum Tcomp in this compost able to induce this systemic effect. However, unidentified chemical factors in compost are also responsible for this suppressive activity.

Results of two consecutive years on mould prevention in viticulture by means of UV C application of vines (Vitis viniferaL.)

In the last decade, impacts of climate change on cool climate viticulture were most obvious concerning cluster infections caused by Botrytis cinerea , the causal agent of grey mould. The control of primary and secondary fungal pathogens is economically most important since bunch rot may severely affect the annual harvest with regard to quality and quantity. Trials with UV C applications, a new approach to control bunch rot, were conducted in 2013 and 2014, representing years with intensive bunch rot epidemics. UV C irradiation was applied by a prototype at an experimental site of Hochschule Geisenheim University. At both canopy sides, leaves and cluster zones were irradiated repeatedly at a dose of ≤160 mWs/cm2 alone or in combination with chemical control. The results of our experiments indicated that irradiation with UV C, in addition to fungicide treatments at reduced number of applications, was able to significantly decrease infection with grey mould to a degree of efficiency of 82% compared to standard chemical treatment that achieved 51% efficiency in 2014. Accordingly, the new technology is suitable for reducing cluster infection with mould fungi allowing a prolonged grape ripening time, which leads to a better harvest quality and a decreased yield loss.

The ‘Dr Jekyll and Mr Hyde fungus’: noble rot versus gray mold symptoms of Botrytis cinerea on grapes

Many cryptic species have recently been discovered in fungi, especially in fungal plant pathogens. Cryptic fungal species co-occurring in sympatry may occupy slightly different ecological niches, for example infecting the same crop plant but specialized on different organs or having different phenologies. Identifying cryptic species in fungal pathogens of crops and determining their ecological specialization are therefore crucial for disease management. Here, we addressed this question in the ascomycete Botrytis cinerea, the agent of gray mold on a wide range of plants. On grape, B. cinerea causes severe damage but is also responsible for noble rot used for processing sweet wines. We used microsatellite genotyping and clustering methods to elucidate whether isolates sampled on gray mold versus noble rot symptoms in three French regions belong to genetically differentiated populations. The inferred population structure matched geography rather than the type of symptom. Noble rot symptoms therefore do not seem to be caused by a specific B. cinerea population but instead seem to depend essentially on microclimatic conditions, which has applied consequences for the production of sweet wines.

Effects of Ozonated Water on Storage Life and Postharvest Quality of Iranian Table Grape (cv. Bidaneh Qermez)

Grape as a perishable fruit is susceptible to fungal infection especially Botrytis cinerea, as an agent of gray mold, and berry dehydration. There are limitations in use of synthetic chemical compounds to control postharvest losses in grape and other fruits. The aim of this study was the evaluation of non-chemical and safe methods for this purpose. Therefore, ozone soluted at 0.3 ppm concentration with three treatment times (5, 10 and 15 min), in water was applied on ‘Bidaneh Qermez’ grape cultivar. Qualitative characteristics (decay, vitamin C, reducing sugars, weight loss, berry abscission, dehydration, cracking and sensory analyses) were evaluated. The results showed that treated fruits with ozone had lower decay percentage, weight loss, berry dehydration, abscission, cracking and higher reducing sugars and storage quality compared to controls. As a general result, ozone treatment caused lower decay incident and longer storability.

STUDY ON THE EFFECTS OF CHITOSAN IN PRESERVING SOME QUALITATIVE FACTORS OF TABLE GRAPE (VITIS VINIFERA 'SHAHROUDI')

Grape as a perishable fruit is exposed to fungal infection especially Botrytis cinerea as an agent of gray mold, therefore its storage life is very short. Currently, gray mold is controlled by canopy management, preharvest fungicide applications and postharvest sulfur dioxide fumigation. However, alternatives to sulfur dioxide are desirable because it can cause bleaching of the berries and browning of the rachis, and its residues can be harmful to people allergic to sulfites. Chitosan, a natural biopolymer with antifungal and eliciting properties is able to reduce postharvest decay of table grapes. 'Shahroudi' table grapes, undergoing deterioration were selected as model fruit with Botrytis cinerea, to test the antifungal activity of chitosan. In this paper, the effectiveness of two concentrations of chitosan (0.5 and 1%) to control postharvest decay and quality of 'Shahroudi' grape berries stored at 0-2°C were investigated. Chitosan treatment significantly reduced postharvest fungal decay of the fruit infected with B. cinerea compared to controls. Differences in weight loss, color change, ripening and sensory quality between grapes treated with chitosan and control fruit suggested that chitosan had antifungal activity. Moreover, the sensory analyses revealed beneficial effects in terms of delaying rachis browning and dehydration and maintenance of the visual aspect of the berry without detrimental effects on taste or flavor.

Ability of the antagonistic yeast Cryptococcus albidus to control Botrytis cinerea in strawberry

The yeast Cryptococcus albidus, originally isolated from mature strawberry fruits, was tested for antagonistic activity against Botrytis cinerea, the causal agent of grey mould in strawberries. Conidial germination and germ tube growth of conidia of B. cinerea were inhibited by a cell suspension of the antagonist in aqueous strawberry fruit pulp suspension (1%) after 6 and 24 hours of incubation. Application of a cell suspension (1 × 106 cells/ml) on detached strawberry leaf disks incubated at 10°C reduced incidence and conidiophore density of B. cinerea by 86 and 99%, respectively, but effectiveness was reduced at higher temperatures. Treatments with C. albidus during bloom of strawberries reduced incidence of grey mould on ripe strawberry fruits after harvest by 33, 28 and 21% in three years of field trials. The effectiveness of the yeast was increased when formulation substances (alginate, xanthan and cellulose) were added to the cell suspension.

Development of a dot blot technique for rapid identi®cation of Botrytis cinerea, the causal organism of grey mould in greenhouse tomatoes

SummaryA dot blot assay, based on the internal transcribed spacer of the ribosomal region, was developed for rapid diagnosis and identification of Botrytis cinerea, the causal agent of grey mould of greenhouse tomatoes. In this assay, DNA from fungal cultures and diseased plant tissue were amplified by PCR using primers specific to septate fungi, fixed to nylon membranes, and hybridized with digoxigenin-d-UTP labelled oligonucleotides specific to B. cinerea. The hybridized probes were detected by chemiluminescence. Six isolates of B. cinerea, four isolates of Botrytis species, one isolate each of B. fabae, B. squamosa, B. streptothrix, B. allii, B. porri, and B. tulipae and some common greenhouse pathogens were tested using this assay. Of four probes screened, probe Bot1 gave a positive reaction with all isolates of B. cinerea and with fresh or frozen plant tissue affected with grey mould from research centres and commercial greenhouses. All other greenhouse fungi tested negative with probe Bot1. This dot blot diagnoses infection by B. cinerea in large numbers of samples rapidly and reliably and distinguishes isolates of B. cinerea from other epiphyte fungi found on greenhouse crops.

Biolistic transformation of conidia of Botryotinia fuckeliana

Botryotinia fuckeliana, the causal agent of grey mould, was biolistically transformed to hygromycin B resistance using a plasmid (pOHT) containing a bacterial hygromycin phosphotransferase gene fused to regulatory sequences from Aspergillus nidulans. Multiple copies of the plasmid, precipitated onto tungsten particles, were delivered into the conidia by a helium-driven gene gun. Southern analysis showed that the plasmid was integrated into the fungal genome at one single locus. After five subsequent transfers on selective medium, all transformants were mitotically stable. When propagated on non-selective medium, four out of eight transformants retained their resistance to hygromycin B. Southern analysis of the fifth generation of transformants showed that no genetic rearrangements occurred during vegetative growth of stable transformants.